After the EPO kicked in, I rode a 200-miler and I felt strong, fresh, ready to hammer. The next day I easily could have ridden another 200.

"OK," the doctor said when we settled into his examination room. "What do you want to be?"

I looked confused, so he explained.

"You want to be bigger? Leaner? Faster longer or faster shorter? More overall endurance? You want to see better?"

"See better?"

"Human growth hormone does that for some people. It improves the muscles in the eyes." He tried again: "So, what do you want?"

This was quite a concept. Freud wrote that anatomy is destiny, and here was a doctor giving me a chance, in my late forties, to alter my body in the most fundamental way. It was strange, but also strangely alluring.

It had taken me a while to arrive at this moment. I was sitting in the San Fernando Valley offices of a physician whose identity I've agreed to conceal—let's just call him Dr. Jones. For reasons I'll explain shortly, my goal was to experience firsthand some of the banned performance-enhancing drugs that are often abused in the endurance sports I participate in, like cycling and cross-country skiing. The menu I had in mind included human growth hormone (HGH), testosterone, and some variety of anabolic steroid, all of which are used to increase strength and shorten an athlete's recovery time by repairing muscle cells faster. Also high on my list was that powerful stuff called erythropoietin, better known as EPO, a hormone that boosts oxygen levels in the blood by prompting the bone marrow to produce more red blood cells. EPO is known to have amazing endurance-boosting effects; not surprisingly, it's been a scourge for years in professional biking and skiing. In 1998, to cite one famous example, the Tour de France nearly came to a halt when a leading team, Festina, was caught using EPO, HGH, steroids, and testosterone. The entire squad was disqualified, and dozens of riders either staged protests or withdrew in reaction to the drug tests and police raids that followed.

All of these are prescription drugs, and they all have legitimate medical applications. (HGH, for instance, is used to treat Prader-Willi syndrome, a rare disease that stunts the growth of children.) But you and I are not supposed to have them without a doctor's supervision, and they're absolutely forbidden in most higher realms of sports. There are exceptions—Major League Baseball doesn't drug-test at all—but if you were caught using these substances in, say, the Olympics, the Tour, the NFL, or any NCAA event, you would face disqualification and suspensions, though the penalties and the testing processes vary wildly. This is one of the key problems that the World Anti-Doping Agency (WADA), an independent drug-policy group headquartered in Montreal, is attempting to address—with the goal of standardizing everything from a list of banned drugs to the testing-and-appeals process. WADA's hope is that these rules and procedures will be adopted by sports federations around the globe.

When I first began my quest, I'd assumed it would be easy to slide into the underground where performance drugs are bought and sold. But when I asked around, nobody, not even friends who were top amateur and professional athletes, knew where cheaters actually went to score. Their comments were always vague: "Well, they get it, believe me," they'd say, or "How about the Internet?"

So at first I just hit the streets. I live in Santa Monica, California, and I started going to Gold's Gym in nearby Venice, the place that launched Arnold Schwarzenegger and other bodybuilding greats. At Gold's you can easily meet gym rats who know where to find muscle-enhancing goodies, and after a few weeks of hanging out, I found myself sitting in a beat-up sports car with one of my new lifting buddies, a beefy guy in his early thirties who showed off his stash with unveiled excitement.

"Look, here's a good thing to start with," he said.

He handed me a bottle of pills. It was Stanozolol, an anabolic steroid that lifters use to add muscle mass. This is one of the drugs that sprinter Ben Johnson was caught using at the 1988 Summer Olympics in Seoul, where he was subsequently stripped of his 100-meter gold medal.

"Where do you get this?" I said.

"A vet I know," he answered casually. It took me a second to realize he meant veterinarian, not military veteran. "Vets and Mexican farmacias, that's where you get the best stuff." I looked at the label on the bottle—these were literally animal pills. They're used to bulk up livestock, and they're banned from greyhound racing, where they're given to dogs to make them stronger.

"Start with this," he went on, spilling out several doses. "Good base, can't go wrong." I must have looked shocked, because he gave me a friendly punch in the arm and said, "You want to get big, don't you?"

That night at home I sat staring at the pills. Veterinarians? Mexican pharmacies? I shuddered and threw them out. I knew the only way I could play this game was under a doctor's supervision.

THAT'S WHAT LED ME, a few weeks later, to Dr. Jones. He was an internist by training and a specialist in the hot new field of anti-aging medicine, which involves helping people—who are always affluent, since these treatments are expensive—try to stave off the effects of growing old with a combination of nutrition and drugs, including HGH, steroids, and testosterone. A doctor I knew had tipped me off, with a wink, that Dr. Jones also used these drugs to "work with a lot of athletes."

Inside his waiting room, I'd squeezed in next to the World's Largest Man and a woman who I thought might be an actress—though I couldn't be certain, since she was wearing a hat and sunglasses indoors. The jumbo guy was somebody I was pretty sure spent Sunday afternoons chasing quarterbacks on television. Such people were, I would come to realize, the core of Dr. Jones's business: athletes and attractive women of all ages. Plus rich guys over 50. And the odd Playmate or two. Oh, and me.

Dr. Jones was an intense guy with a wiry build, close-cropped dark hair, and Al Pacino's restless energy. He ran a small, boutique operation: high service, high price. (I ended up spending around $7,500 for drugs in my eight-month program.) Dr. Jones knew what I was up to and agreed to help me try the drugs in a safe manner. What he did for me—supplying drugs solely for the purpose of increasing my athletic prowess—is not illegal, but it would certainly be frowned on by many of his colleagues. For that matter, many of them disapprove of the whole notion of anti-aging medicine, believing these drugs should be used only to fight specific maladies, not the natural process of aging.

But that doesn't bother Dr. Jones. He takes anti-aging drugs himself, and in his rapid-fire style, he told me he wasn't in the "sickness" business, as he described the work of ordinary doctors. He was in the "improvement" business.

NO ONE KNOWS how long athletes have taken supplements, but it's been going on quite a while, since well before the modern era of drug manufacture. The coca leaves that South American runners used for centuries provided a natural boost. Back in the early 1900s, when racers in the first years of the Tour de France ate bull testicles as snacks, they were simply trying to increase their testosterone levels.

According to sports historians, the use of drugs in athletics appears to have been routine by the post-World War II era. Amphetamines were the favored way to improve endurance, while steroids were the muscle builder of choice. At the Olympic level, abuse was rampant, and it wasn't until the 1968 Summer Games in Mexico City that any rudimentary drug testing was enforced, largely in response to the obvious doping going on by Eastern Bloc teams. Much later, in the breakthrough 1998 lawsuit that several hundred former East German athletes brought against their trainers, doctors, and coaches, the "vitamin" regimens they were duped into following—in fact, they were given steroids—were compared to torture by the Nazis. East Germany's state-supported system of doping, which often began before puberty, left a legacy of Olympic medals—along with deformed offspring, heart attacks, facial disfigurement, and lifelong sexual dysfunction. Sometime in the late 1970s, what was called "blood packing" began to supplement amphetamines. More red blood cells translates into more oxygen being distributed throughout the body, thus resulting in increased endurance. This was before EPO, and in those days blood was drawn, usually by team doctors, spun in a centrifuge to increase the concentration of red blood cells, and reinjected into the body.

This worked just fine until a certain line was crossed—different in every individual and hard to predict—and thickened blood started turning to sludge. Heart attacks and strokes followed. Athletes would mysteriously die in their sleep, because their lowered heart rates were unable to pump the enriched, heavy blood. According to Dutch media reports, from 1987 to 1990, 17 Dutch and Belgian professional cyclists died as a result of abusing EPO.

Because no foreign substances were involved, blood packing was considered legal, if unethical. At the 1984 Los Angeles Olympics, eight U.S. cyclists, including gold medalist Alexis Grewal, gave themselves transfusions of previously frozen packed blood inside their hotel rooms before competing in the 118-mile road race. The International Olympic Committee tested the riders, detected the doping, and briefly covered up the results before announcing, in 1985, that new rules were being written to ban any "artificial" means of altering one's blood chemistry.

When EPO emerged in the late eighties, blood packing became passé. EPO occurs naturally in the body, but only in tiny amounts. Researchers at Amgen Inc., a California pharmaceutical company, figured out how to synthesize it in quantities that could help people who weren't producing enough red blood cells, like cancer patients suffering from anemia. EPO was also a gift from the gods for athletes looking to cheat. It was easy to administer—a clear liquid injected with simple shots—always effective, and, until recently, impossible to identify, because there was no chemical test to alert doctors to its presence.

The difficulties of detecting EPO finally drove anti-doping officials to decree that they would disqualify any athlete found with a red-blood-cell concentration—known as the hematocrit level—of more than 50 percent. (The hematocrit level for an ordinary, active person is between 34 and 46 percent.) Of course, the 50 percent mark only gave athletes a defined limit. You could use EPO to jack up your levels higher than that while training, and as long as you competed with a level of 49.9 percent, you'd be fine.

It wasn't until the Sydney Olympics in 2000 that anti-doping experts, led by Françoise Lasne, a researcher at the French National Anti-Doping Laboratory, had come up with a method to distinguish the red blood cells produced by EPO from those produced naturally—enabling chemical detection of the drug. But each year, with new generations of drugs, cheating becomes more sophisticated, and EPO isn't the only substance that boosts red-blood-cell production.

Johann Muehlegg, the German cross-country skier who in 1999 left Germany's team to race for Spain, relied on a drug called darbepoetin—a genetically engineered version of EPO—to raise his levels at the Salt Lake Games. He won three individual races: the 30-kilometer freestyle, the 10K pursuit, and the 50K classic. When his darbepoetin use was detected by a chemical test before his third win, he defended taking it, since the drug, at that time, was not officially banned. Under the tortured rules of the Olympics, he was allowed to keep his 30K and 10K golds, which he won before he was tested, but had to return the 50K medal, which he won afterward.

Great. As if you could race dirty on Saturday and clean on the Monday before. Obviously, the playing field is still not very level.

THE ABUSE OF DRUGS IN SPORTS has been an interest of mine for years, but it wasn't until the mid-eighties, when I started competing as an amateur in cross-country ski races in Europe, that I was suddenly immersed in a world with two classes of racers: athletes who played clean, and those who didn't.

The Swedish skiers I hung out with back then, some of the best long-distance skiers in the world, were all convinced that the Finns were the worst Scandinavian cheaters, and they appear to have been right. In 2001, following a series of positive doping tests at the World Championships, almost the entire Finnish men's team was suspended, and the country's men's and women's coaches were banned from international competition for life.

It was maddening to see skiers I knew to be playing fair, guys who trained their hearts out with little financial reward, lose to the cheaters. Over the years, it only got worse, the drugs more potent, the means of evading detection increasingly devious. Every time one of my athletic heroes tested positive, I was furious, as if I'd been personally betrayed.

But there was another feeling, too: deep curiosity. I'd read reams about cheating as an issue, but I'd never read anything describing what it felt like to do it. Obviously, the allure of victory was incredibly powerful—why else would the best athletes in the world risk their health and lives abusing these drugs? So I wondered, Do performance drugs make you just 1 percent faster and stronger? Or 10 percent? Are the enhancements so subtle that only elite athletes gain an edge, or are they powerful enough that an everyday wannabe like me would notice a dramatic change?

Though I knew I would be courting health risks, I decided there was only one way to find out: try it myself, and see what it did.

My plan was simple. I would train as I always do—about 15 to 20 hours a week—while taking various supplements under Dr. Jones's supervision. I started in January 2003. In eight months, I intended to ride the 1,225-kilometer (761-mile) Paris-Brest-Paris bicycle race, a once-every-four-years sufferfest that's popular among amateur ultracyclists. I would first have to qualify by completing a series of 200-, 300-, 400-, and 600-kilometer rides within certain time limits. The PBP was a quirky event, a ride rather than a real race, with no prizes, no ranking of finishers, no doping controls. So if the drugs helped me, I wouldn't be knocking anybody else down in the standings. And since this was a monster ride—which I'd have to complete in less than 84 hours—it would serve as a real test of my augmented self.

THE ONLY REMAINING question: Where to begin?

"Let's start with human growth hormone," Dr. Jones announced that first day in his office. I wasn't surprised. HGH is the foundation of his anti-aging regimen, and it's one of the hottest banned supplements in sports. It's a protein produced by the pituitary gland that's involved with various strength- and growth-related body processes, including normal growth during childhood, adult sexual function, bone strength, energy levels, protein formation, and tissue repair.

"Between 20 and 30 years of age," Dr. Jones explained in a long, impressive presentation, complete with fancy computer graphics, "our growth hormone is at its absolute peak. And then all of a sudden, it drops."

It was the bit about "reduced exercise performance" that athletes seized on in the mid-nineties. If lower HGH levels hurt performance, the reasoning went, then higher levels would help it. And while there are sophisticated tests for steroids, there is still no means to detect HGH. It was so widely abused at the 1996 Summer Games in Atlanta that athletes joked about renaming them "the Human Growth Hormone Olympics." Dr. Jones started me out small, with only 0.1 international units a day, five days a week—about what he would give a Rodeo Drive matron. (The international unit, or IU, is a worldwide standard calibrating the effective dosages—which vary in volume depending on the drug—for substances like hormones and vitamins.) I told him I wanted more, and I wanted more than just HGH.

"We have to introduce one at a time," he said firmly. "That's the only way to monitor what each does. We start slowly and build."

I asked him what to expect.

"I really can't promise you anything about the growth hormone except that it costs a lot of money," he said with a smile. (My HGH cost about $750 a month.)

"Do you take it?"

He nodded. "I take a lot of things."

"What does it do for you?"

"That doesn't matter. It may do something for me, nothing for you—it's very response-specific." He warned me not to expect too much, too fast. "Nothing will happen very quickly. This is a gradual process."

I didn't listen, of course, or believe. Who would? For the first time in my life I was injecting a foreign substance into my body, and it was simply impossible not to expect swift and dramatic changes. Dr. Jones showed me how to prep my leg with a prepackaged alcohol pad, then load the syringe with 0.1 IU of HGH, painlessly sliding in the ultrathin needle.

"My 81-year-old mother does this, so you can, too," he said when I flinched at the idea. "It's no different from what diabetics do every day."

Yeah, except that it seemed so wrong—and so bizarre.

ON THE WEEKEND OF MARCH 1, after only a few days of treatment, I traveled to Furnace Creek, California, and rode in the Death Valley Double Century. I didn't feel very augmented: The race was a minor disaster, and I limped over the finish line so late that they were timing by calendar, not stopwatch. I felt disappointed not just in my performance but, oddly, in my drug.

I was soothed a bit the next week when I went in for my first follow-up with Dr. Jones. I handed his nurse the stylish silver kit I'd been given to house my HGH bottles and syringes so that she could safely dispose of my used needles.

"You're not using the growth hormone?" she asked, puzzled.

"Sure I am. For two weeks."

She held up a small vial with an unbroken seal. "This is the growth hormone. It hasn't been opened."

I pointed to a large vial filled with red liquid. "That's what I've been injecting." Then a quick burst of panic. "What is it?"

"Don't worry. It's vitamin B12. We use it to mix with the growth hormone. This is just the extra B12 we didn't use yet. Don't worry, B12 is good stuff. Gives you more energy."

"I'm an idiot."

"The growth hormone does help with cognitive functions," she said cheerfully. "They're starting to use it with early Alzheimer's."

After a few weeks of the HGH, I began to notice subtle changes. My skin started getting... better. Sun blotches that I'd had on my arms for a year faded away. One morning I woke up and a scar on my forehead—which I'd gotten from a mountain-bike endo two years earlier—was more or less gone. Even though I was training like a madman, I looked more rested. Younger. A little fresher.

Then I started to realize that my eyesight really was improving. I'd been thinking about getting glasses to read fine print on maps, but now there was no need. The glasses I used for night driving stayed in the glove compartment, unused, unnecessary.

Dr. Jones had a specific protocol he wanted to follow, partly for safety reasons and partly so I could discern what each drug was doing. After the HGH, he added testosterone, giving me a 200-milligram injection and a pump vial full of Testocream, white stuff that I rubbed on the sides of my stomach. "It's like with a bathtub," Dr. Jones explained. "The shot fills the tub. The cream keeps replenishing it every day to top it off."

For most men—and women—testosterone production peaks in your twenties and slowly declines. Testosterone urges the RNA, or message center, in muscle cells to create more protein, hence more muscles. Higher testosterone levels have been shown to increase energy and aggression, in both men and women. Anti-aging types believe that testosterone decline is a big factor in the loss of muscle and the increase in fat that are standard signs of getting older. Not to mention a loss of libido. There can be side effects from taking it—ranging from acne to high blood pressure—but the drug's many fans think the trade-off is worth it.

I walked out of Dr. Jones's office smiling broadly, then waited for a werewolf surge. And I waited. But the truth is, I didn't feel much of anything. No irresistible bursts of lust or rage, no particular feelings of omnipotence. That afternoon I went home and celebrated my newfound energy and aggression with a long nap.

IT WASN'T UNTIL I ADDED EPO to my diet, two weeks later, that I began to notice serious differences.

"You have to be careful with this stuff," Dr. Jones warned after explaining the routine: three injections a week of 1,500 IU each. I was expecting a lecture on the dangers of thickened blood, but he meant something else: he wanted me to take it easy while racing, lest people catch on.

"One of my bike racers who isn't really a climber went on a training ride and dropped the best climbers on his team," he said. "They were like, 'Um, what are you taking?'"

It wasn't cheap—$2,000 for ten vials totaling 100,000 IU. At my prescribed dose, each vial would last two weeks. Before the first EPO shot, my base hematocrit level was 43.8 percent, well below that magical 50 percent disqualification level. That seemed like a reasonable goal—hematocrit levels high enough to be bounced from the Olympics. Sweet.

The morning after I took my first dose, I woke up with a strange headache, a very distinct kind of pain that I would come to associate with EPO. It defied all manner of ibuprofen and aspirin but gradually went away.

Within three weeks, my hematocrit level had risen to 48.3. By this time, my testosterone levels had shot up to 900 nanograms per decaliter, from a previous mark of 280. (My starting level was just below normal.) My HGH had increased only slightly, which Dr. Jones found unusual. He upped my HGH dosage to 1.2 IU a day, speculating that the long hours I spent training might be keeping the level down.

Despite these measurements, I remained skeptical about all the drugs until March 29, when I rode an event along the central coast of California, the Solvang Double Century, at what for me was a fast and hard pace, finishing in around 11.5 hours. About ten hours in, it dawned on me that something was definitely happening. Sure, I'd been training hard, but I'd done enough of that to know what to expect. All around me were riders—good, strong riders—who looked as worn out as you'd expect after ten hours in the saddle. I was tired, but I felt curiously strong, annoyingly talkative and fresh, eager to hammer the last 40 miles. The last time I'd ridden 200 miles, I felt awful the next day, like I'd been hit by a truck. After the Solvang race I woke up and felt hardly a touch of soreness. I also felt like I could easily ride another 200, and I realized that I'd entered another world, the realm of instant recovery. I'll be frank: It was a reassuring kind of world, and I could see why people might want to stay there.

When I checked in with the good doctor soon after the race, he wasn't surprised about what I'd experienced. "With your hematocrit levels higher, you don't produce as much lactic acid, which means you can ride harder, longer, with less stress. The growth hormone and testosterone help you recover faster, since you're stronger to start with and recover more quickly. All those little muscle tears repair much more quickly."

He shrugged. "It works," he said. "It always works."

It all started to make sense. Feeling like I did after the 200-miler would be a huge advantage in a long stage race like the Tour de France. I understood what five-time Tour winner Jacques Anquetil meant back in 1967 when he said, "You'd have to be an imbecile or a hypocrite to imagine that a professional cyclist who rides 235 days a year can hold himself together without stimulants."

Back then, "stimulants" mostly meant amphetamines, which kept riders going through day after day of hard stages. The new drugs had the same rejuvenating effects but simply worked much better, without the crash and depression of uppers.

I began to adjust my training schedule for harder rides and less rest and I felt fine. It wasn't a huge difference—I added about 10 or 15 percent more effort to my training—but had I been competing at a top level, it would have represented a major advantage.

A MONTH LATER, when I added a basic anabolic steroid to the mix, I felt like I'd grabbed on to a car moving at 60 miles an hour. The effect was powerful, fast, and difficult to modulate.

Dr. Jones gave me a steroids tutorial over lunch one day, at a Middle Eastern place on Ventura Boulevard. He explained how "steroids" is a broad term for various synthetic substances related to the male sex hormones, and that they promote the growth of skeletal muscle and the development of male sexual traits. Though each steroid has different effects, they generally increase the amount of nitrogen in the body, which in turn stimulates protein synthesis.

All of which is a fancy way of saying that steroids help the body create muscle. They're used medically to treat everything from anemia to leukemia to AIDS, helping patients build strength.

Dr. Jones took out a pen and drew a chart on the paper tablecloth. On one side he listed various kinds of steroids: Anadrol 50, Winstrol, Deca, Anavar. Then he added columns labeled MASS, STRENGTH, WATER GAIN, RETENTION. For each drug, he filled in a number from one to a hundred.

"What you want is something that doesn't give you a lot of mass but adds strength," he said. "I'd start with Deca. It has almost no liver toxicity and has the nice benefit of helping joint pain. In Europe, it's used for arthritis. There's only one reason everybody doesn't use Deca."

"You grow two heads?"

"Worse, at least for most athletes. You can test positive for up to a year."

I stared at the chart, fascinated. Then it struck me that there was no column for side effects, nasty little consequences like liver damage, impotence, and steroid rage. I asked Dr. Jones about this.

He sighed and gestured along the wide table. "We don't have enough room to list them," he said. "The problem with steroids is that they do have some benefits, but nine out of ten people who are drawn to them can't resist abusing them. Then there's all the black-market junk out there. I'm not going to lie to you and tell you that if you try this stuff a little, it will kill you. It won't. But you stay on it very long and you'll have problems."

"Like?"

"Your hair may start to fall out. Your testicles shrink. Of course, the testosterone can cause all that, too. But any steroid will accelerate it.

"Deca's not so harmful to your liver," he went on, "but most steroids can knock the hell out of it. You can get huge mood swings. Anger, irritability. Sex is a mess. There's a surge in libido, then it falls off a cliff and you don't even want to think about sex. Then, when you stop your dosage, you start to shrink. Depression can set in. Your body starts to slide back to what it was, and most people don't like that. People forget that it's the drugs and not them. It's like when you take Viagra and you think that's how you'll always perform. No, no, no."

All the same, I wanted to try it.

"If you want to try 200 milligrams of Deca for a limited time, coming back to my office every week, OK," said Dr. Jones. "It'll probably help your shoulder, if nothing else." My left shoulder had been hurting for a year since a bike accident. He explained that Deca helps the joints retain water, which eases pain.

Throughout this experiment, I'd been e-mailing people whom I'd encountered on various Web sites, like Extreme-Athlete.com, where steroid users get together and compare notes. That night I went to one of the bodybuilding sites I'd joined and listed what I was taking: the HGH, the testosterone, the EPO, and now the Deca. I thought I was really pushing the limits, but, tellingly, I was immediately mocked for my timidity and puny dosages.

"Dude, why not just take aspirin?" wrote a guy who called himself the Great One. "Try like 600 milligrams of test and 400 to 600 of Deca a week, girlie boy. And what's with this human growth stuff? My mom takes that. Why not Dianabol?" he wrote, referring to a particularly potent anabolic steroid. "You afraid of getting strong?"

It was standard practice on these sites to close messages with a quote or a quip like "I may die, but they'll need a big coffin." The Great One signed his with a thought from Nietzsche. "Everything that elevates an individual above the herd and intimidates the neighbor," it read, "is henceforth called evil."

ONCE I STARTED THE DECA, I didn't even think about lifting weights. I wanted to get stronger, not bigger. Within two weeks, the pain I felt in my left knee after 100 miles or so—100 was now just a standard ride—went away, coming back only on the most brutal hills. My shoulder felt much better. And then one morning I stepped on the scale.

Two hundred and nine pounds.

I was stunned. I'd never weighed this much. When I first saw Dr. Jones, I weighed 195, which was high for me.

Immediately I hopped on the bike and rode like hell for a few hours. When I got back, I stepped on the scales: 201. I'd lost eight pounds on a not very hot day when I was drinking plenty of fluids?

"What's the problem?" Dr. Jones demanded when I told him I was freaking out over the weight gain. He had me stand on a machine that measured body weight and fat. I weighed 207, but my body fat had dropped to 6.5 percent, down from 10 percent.

"Don't give me this you're-getting-fat crap," he said in an exasperated tone. "You sound like some teenage girl. You've lost six pounds of fat and gained 12 of muscle. That's why you're heavier. And like I told you, the Deca supersaturates the muscle cells with fluid. That's one of the reasons your joints feel better."

At this point my little adventure started to feel pretty creepy, as if there were something inside my body taking over. Which, in a way, there was. I was getting big without trying. When I went for ocean swims, I had trouble getting into my wetsuit. I didn't look cut, though—it was more of a puffy, rounded bigness, making me look like a shorter version of Shaq. Without a jump shot. I did my final 600K qualifying ride for Paris-Brest-Paris on June 15, out of Princeton, New Jersey. This was 200 kilometers farther than I'd ever ridden. By now my HGH levels were 20 percent higher than when I'd started. My testosterone was 300 percent higher. My hematocrit level hovered around 50 percent. I weighed 205—a ten-pound gain—but my body fat was the lowest it had ever been.

We left Princeton at 4 a.m. on a misty, muggy morning. It was a strange course. The first 200 was flat and easy, then came 200 killer kilometers that involved 12,000 feet of climbing, then another fairly hilly 100 and a flat final leg. The whole thing would take me about 31 hours.

I'd been overseas the week before and was tired and jet-lagged at the start. During the easy section, I dragged along, barely staying awake. But when we moved into the hills, I started to feel stronger. I wasn't fast up the hills—but then, I never had been. My weight gain was a hindrance, but I had deep reserves of power and endurance. I rode through the darkness with an image of myself as some kind of tank, just moving along, unstoppable.

At 2 a.m., we took a break at a convenience store in Easton, Pennsylvania. It was Saturday night and the place was filled with kids coming and going to parties and dates. I got a glimpse of myself in the glass of a freezer door. I had a light on my helmet and a bunch of other blinking gizmos attached to my arms and ankles. My face looked like one of those "thousand-yard stare" photos from Vietnam.

What have I done? I wondered. I had a life once, and now I'm standing in the Easton WaWa in the middle of the night, looking like a cyborg, with thousands of dollars of drugs coursing through my veins. I started looking forward to the moment when the whole thing would be over.

THE WEEK BEFORE I arrived in France, it was more than 100 degrees, and people were dying all over the country. But a few days prior to the August 19 start of the PBP, the weather broke, and the ride started at 5 a.m. in a light chill. Perfect cycling weather.

I was riding a tandem bike with my pal Bob Breedlove, an ultracycling legend from Des Moines, Iowa. Bob called me out of the blue in June and said he wanted to do the PBP on a tandem—as he had three times before—but that his regular riding partner had bailed. Bob liked to ride long and fast; he'd celebrated his 50th birthday the previous summer by riding across the United States in nine and a half days.

About five hours into the ride, Bob mentioned casually that he preferred doing the race on a tandem, because the heavier bike made it so much more difficult. "A course like this is terrible for a tandem," Bob said happily. "All the hills! You'd do it much faster on a regular bike, no doubt about it."

But we muddled through. I felt shockingly strong until the final 200 kilometers, when my stomach started to shut down. Unaccustomed to the aero bars on the tandem, I'd also developed agonizing saddle sores. These were typical woes of ultrariding, but through it all, my legs and heart felt fine. Five months earlier, I couldn't have imagined riding this far and feeling so strong. We finished the 1,225-kilometer ride in just under 76 hours—sleeping only twice for a few hours. The next morning, if it weren't for my saddle sores, I could have easily done it again. Obviously, Dr. Jones's program had worked.

I'd started months earlier with the goal of using the performance enhancers to complete the PBP. Now that it was over, I was relieved. When I got back from France, I immediately quit everything: no HGH, no testosterone, no EPO, and, God knows, no steroids. It was wonderfully liberating to be freed from a routine that had started out feeling illicit and interesting but had become just an annoying daily chore, like taking vitamins.

Since then, I haven't had my hematocrit level checked, nor my body fat, HGH, or testosterone. But already my eyesight is starting to slip a bit and I find myself squinting to read small type. I'm sure my recovery times from a hard workout have increased. Even if I keep training as hard, my endurance will drop. LOOKING BACK On the whole saga, I find myself wondering whether I'd keep taking these drugs if I could afford them.

For me, it would be a quality-of-life question, not a performance issue. If the HGH weren't so expensive, I'd probably continue with it, at least until I had a good reason not to, like some new evidence that it makes you grow extra ears. (The side effects of HGH are reportedly mild—one is fluid retention.) If nothing else, it helped my eyesight, and I had more energy. Lately, I've been reading studies about how endurance athletes suffer from low testosterone, which leads to early signs of osteoporosis, so I'm going to continue to monitor my levels and, if they drop too far, consider boosting them with the cream.

With the EPO, even if somebody gave it away, I wouldn't go down that road. Using it is too much of a literal and figurative headache, and if you get sloppy there's always the danger of nasty results. And I would never touch steroids again, unless I had some specific medical need. It's all just too powerful, too strange, and it's hard to read a list of the side effects and not feel like you're playing Russian roulette.

As for the larger issue of drugs in sports, eight months in the world of the artificially enhanced convinced me more than ever that it's critical for an organization like the World Anti-Doping Agency to succeed. This group, founded after the Salt Lake Olympics by Canadian anti-doping leader Dick Pound, represents the most serious international attempt to come to grips with sports doping. WADA is the logical response to an argument that gets aired from time to time: that since cheating is impossible to eliminate, the only recourse is to simply legalize everything—that way, no athlete has a hidden advantage over another, since everyone would be free to try anything that might increase endurance.

Like a lot of powerfully bad ideas, that one has a certain mad logic. But it would turn every sport into a test of how much damage an athlete was willing to risk to improve performance, and would basically force every serious athlete to cheat and risk his or her health. Athletic contests would have a strange life-or-death quality. If we don't keep drugs out of these events, they become freak shows, the athletes like gladiators—with us playing the role of decadent Romans, urging them on.

Besides, on a fundamental level, drugs ruin the simple joy of competition. With drugs in the mix, it's not about the athletes, it's about the chemistry.

Now that I was off the program, I started to think about what I'd train for next. Probably something shorter than the PBP—say, the Canadian Ski Marathon, a two-day, 100-mile event. I got a calendar out and began to work on the training schedule. I'd done the race before and knew it would be long, cold, and brutal.

Sounded fun to me. And this time I'd do it on my own.

1904 Trainers give exhausted American runner Thomas Hicks a mixture of brandy and strychnine to keep him going during the 24-mile Olympic road race. He wins, but subsequently collapses just past the finish line.

1952 At the Winter Olympics in Oslo, Norway, several speed skaters become ill from amphetamines.

1967 British cyclist Tommy Simpson dies near the summit of Mont Ventoux, on Stage 13 of the Tour de France. He had allegedly taken amphetamines and chased the stimulants with brandy.

1968 The International Olympic Committee establishes mandatory drug testing at the Mexico City Olympic Games.

1972 Dr. Bjorn Ekblöm of Stockholm's Institute of Gymnastics and Sports invents "blood packing," which involves removing blood, increasing the concentration of red blood cells in a centrifuge, and restoring it through transfusion.

1976 East German swimmers are deceived into taking anabolic steroids by their coaches and trainers. They win 11 out of 13 swim events at the Montreal Summer Olympics that year.

1983 Seventeen athletes, including two from the United States, test positive for anabolic steroids at the Pan American Games in Caracas, Venezuela, and are disqualified. Eleven others leave the games in protest.

1987 EPO emerges as a doping agent, and over the next three years, 17 Dutch and Belgian professional cyclists die after injecting it.

1988 After winning the 100 meters at the Seoul Olympics, Canadian sprinter Ben Johnson is stripped of his gold medal after testing positive for the steroid Stanozolol.

1996 Irish swimmer Michelle Smith medals four times in Atlanta. Two years later, FINA, the governing body of international swimming, finds her guilty of manipulating a urine sample for an out-of-competition test. Smith is banned from competition for four years and misses the 2000 Sydney Olympics.

1998 Four days before the Tour de France, Willy Voet, a masseur for the Festina cycling team, is caught with 400 vials of performance-enhancing drugs. The team is asked to leave the Tour.

1998 In August, shortly before breaking Roger Maris's record of 61 home runs in a season, St. Louis Cardinals slugger Mark McGwire acknowledges that he has been using androstenedione, an androgenic steroid, for more than a year.

1998 U.S. runner Florence Griffith-Joyner, a three-time gold medalist, dies in her sleep from a heart seizure at 38. It is widely suspected that she used human growth hormone to increase her strength.

2003 Bernard Lagat of Kenya, a bronze medalist at the Sydney Summer Games, tests positive for EPO and is banned from the World Track and Field Championships in Paris. He had planned to run the 1,500 meters.